Distributed locking tracker

ABSTRACT

A solar tracker including a torque tube, a plurality of bearings configured to receive the torque tube, a plurality of piers each configured to receive one of the plurality of bearings, and a lock-out device mounted on one of the plurality of piers and operatively associated with at least one of the plurality of bearings, the lock out device configured to periodically engage and disengage openings formed in the bearings to limit movement of the torque tube and to transfer load from the torque tube to the pier on which it is mounted.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of and priority to the filing dateof provisional U.S. Application No. 63/075,626, filed Sep. 8, 2020, theentire contents of which is incorporated herein by reference.

BACKGROUND Technical Field

The present disclosure relates to solar power generation systems, andmore particularly, to solar tracker systems for preventing damage causedby wind loading while maximizing electrical energy production.

Background of Related Art

Solar cells and solar panels are most efficient in sunny conditions whenoriented towards the sun at a certain angle. Many solar panel systemsare designed in combination with solar trackers, which follow the sun'strajectory across the sky from east to west in order to maximize theelectrical generation capabilities of the systems. The relatively lowenergy produced by a single solar cell requires the use of thousands ofsolar cells, arranged in an array, to generate energy in sufficientmagnitude to be usable, for example as part of an energy grid. As aresult, solar trackers have been developed that are quite large,spanning hundreds of feet in length.

Adjusting massive solar trackers requires power to drive the solar arrayas it follows the sun. As will be appreciated, the greater the load, thegreater the amount of power necessary to drive the solar tracker. Anadditional design constraint of such systems is the rigidity required toaccommodate the weight of to solar arrays and at times significant windloading.

Further, the torsional excitation caused by wind loading exertssignificant force upon the structure for supporting and the mechanismsfor articulating the solar tracker. As such, increases in the size andnumber of components to reduce torsional excitation are required atvarying locations along the length of the solar tracker. With theseconcerns in mind prior systems have typically driven the solar modulesto a position where the loads created by the wind are reduced, but thesetypically come at the cost of energy production. For example, onemethodology drives all of the solar trackers to a flat or 0 angleposition relative to the ground. As can be appreciated, thissignificantly reduces the amount of energy being produced. The presentdisclosure seeks to address the shortcomings of prior tracker systems.

SUMMARY

One aspect of the disclosure is directed to a solar tracker including: atorque tube, a plurality of bearings configured to receive the torquetube, a plurality of piers each configured to receive one of theplurality of bearings. The solar tracker also includes a lock-out devicemounted on one of the plurality of piers and operatively associated withat least one of the plurality of bearings, the lock out deviceconfigured to periodically engage and disengage openings formed in thebearings to limit movement of the torque tube and to transfer load fromthe torque tube to the pier on which it is mounted.

Implementations of this aspect of the disclosure may include one or moreof the following features. The solar tracker further including a camshaft driven synchronously with the torque tube. The solar trackerfurther including at least one cam mounted on the cam shaft and engagingthe lock out device. The solar tracker where the cam includes aeccentric groove configured to receive a follower of the lock outdevice. The solar tracker where the follower is rigidly affixed to ashaft support. The solar tracker where the shaft support is mounted onthe pier via a hinge. The solar tracker where one or more pins affixedto the shaft support are configured to engage one or more openingsformed on the bearing. The solar tracker where, as the cam shaft and camrotate, the follower which engages the eccentric groove causes the shaftsupport to rotate on the hinge causing the pins to engage with ordisengage from the openings formed on the bearings. The solar trackerwhere a pier includes two lock-out devices configured to alternatelyengage and disengage from the openings in the bearing. The solar trackerwhere the bearing is a concentric bearing. The solar tracker where thebearing is a mass balanced bearing. Implementations of the describedtechniques may include hardware, a method or process, or computersoftware on a computer-accessible medium, including software, firmware,hardware, or a combination of them installed on the system that inoperation causes or cause the system to perform the actions. One or morecomputer programs can be configured to perform particular operations oractions by virtue of including instructions that, when executed by dataprocessing apparatus, cause the apparatus to perform the actions.

One aspect of the disclosure is directed to a lock out device for asolar tracker including: a shaft support. The lock also includes a hingeconfigured to connect the shaft support to a pier and allow the shaftsupport to rotate relative to the pier. The lock also includes afollower rigidly mounted on the shaft support. The lock also includesone or more pins configured to engage one or more openings on a bearingto limit rotation of the bearing.

Implementations of this aspect of the disclosure may include one or moreof the following features. The lock out device where the follower isconfigured to be received within an eccentric groove of a cam. The lockout device where rotation of the cam applies force to the follower andcauses the shaft support to move. The lock out device including a pairof shaft supports, each mounted on opposite sides of the pier by ahinge. The lock out device further including two cams, one each onopposite sides of the pier. The lock out device where each shaft supportincludes a follower configured to engage an eccentric groove of a camlocated on a respective side of the pier. The lock out device where thetwo cams are mounted on a cam shaft. The lock out device where rotationof the cam shaft causes the eccentric groove formed in each cam to acton the follower and rotate the shaft support such that the pins on theshaft support engage with or disengage from the openings in the bearing.The lock out device where the eccentric grooves of the two cams causesthe pins on the pair of shaft supports to alternately engage with anddisengage from the openings in the bearing. Implementations of thedescribed techniques may include hardware, a method or process, orcomputer software on a computer-accessible medium, including software,firmware, hardware, or a combination of them installed on the systemthat in operation causes or cause the system to perform the actions. Oneor more computer programs can be configured to perform particularoperations or actions by virtue of including instructions that, whenexecuted by data processing apparatus, cause the apparatus to performthe actions.

BRIEF DESCRIPTION OF THE DRAWINGS

Various aspects of the present disclosure are described herein belowwith reference to the drawings, which are incorporated in and constitutea part of this specification, wherein:

FIG. 1 depicts a side view of a solar tracker;

FIG. 2 depicts a side view of a solar tracker in accordance with thedisclosure;

FIG. 3A depicts a perspective view of a solar tracker bearing fittedwith a lock-out device in accordance with the disclosure;

FIG. 3B depicts a perspective view of a solar tracker bearing fittedwith a lock-out device in accordance with the disclosure;

FIG. 4 depicts a perspective view a lock-out device in accordance withthe disclosure;

FIG. 5 depicts a top view of a lock-out device in accordance with thedisclosure;

FIG. 6 depicts a perspective view of a solar tracker bearing inaccordance with the disclosure;

FIG. 7 depicts a side view of a solar tracker bearing fitted with alock-out device in accordance with the disclosure;

FIG. 8 is a graphical representation of the movement of pins of alock-out device in accordance with the disclosure; and

FIG. 9 depicts a series of frames showing the movement of portions ofthe lock-out device in relation to a solar tracker bearing in accordancewith the disclosure.

DETAILED DESCRIPTION

FIG. 1 depicts a traditional solar tracker 10. The solar tracker 10includes a slew drive 12, connected to a torque tube 14. The torque tube14 receives a series of rails (not shown) attached perpendicular to thetorque tube 14 and upon which a number of photovoltaic solar modules aremounted. The solar tracker 10 also includes a number of piers 16 whichare mounted in the ground on one end and typically include a bearing,for example bearing 20 a or 20 b (FIG. 3A or 3B) but without thelock-out mechanism described in greater detail below. The torque tube 14is received in the bearings 20 and supported on the piers 16. The slewdrive 12 (or other drive mechanism) drives the torque tube 14 and theattached solar modules in an effort to follow the sun as it translatesfrom east to west across the sky.

When windy conditions are experienced, the solar modules act as a sailproviding a face that opposes the wind. The force caused by the windtranslates from the solar modules to the torque tube 14 and to the slewdrive 12. Ultimately the force caused by the wind is translated to theground by the pier 16 on which the slew drive 12 rests. Thus, the forceof the wind collected along the very long solar tracker 10 is ultimatelyconcentrated on a single pier 16. This necessitates the increase in sizeand weight of the slew drive 12 and its pier 16. Further, to preventtwisting of the torque tube 14 along its length, the size and weight ofthe torque tube 14 must also be increased.

The instant disclosure is directed to a solar tracker having havemultiple points of fixity in tracker 100 as shown in FIG. 2 that helpsin preventing torsional instability at all wind speeds and all trackinginclinations. Multiple points of fixity over a length of tracker 100creates favorable conditions for tracker 100 to be stowed, which in turnreduces the pressure load on the solar modules without compromising onstructural stability of the tracker 100.

As depicted in FIG. 2, the solar tracker 100 includes a slew drive 12, atorque tube 14, and a plurality of piers 16. The piers 16, like those ofFIG. 1 support a bearing (not shown) on each allowing for free rotationof the torque tube 14. Mechanically linked to the slew drive 12 is a camshaft 22. The cam shaft may be gear driven or chain driven by the motordriving slew drive 12. Alternatively, the cam shaft may have a separatedrive motor that is configured to drive synchronously drive the camshaft 22. The cam shaft 22 is connected to cams 24, which aremechanically coupled to lock out devices 26 that made with the bearings20 a or 20 b. By locking the bearings 20, the piers 18 which support thelock out devices 26, absorb a portion of any wind loading applied to thetracker 100. This absorption of the load at multiple points along thetracker 100 reduces the load at any one point on the tracker 100 andallow for reduced torque tube dimensions and weight as well asreductions in size of the slew drive. Further, this design enables theelimination of a damper which is typically employed to increase therigidity of the tracker 100 in the torsional direction.

The lock-out device 26 of the disclosure can be deployed on bothconcentric bearings 20 a (FIG. 3A) and mass balanced bearings 20 b (FIG.3B). With respect to the use on concentric bearings 20 a, a bearing base28 is bolted to a top portion of a pier 18 by brackets 30. The bearingbase 28 receives a lower bearing half 32. The lower bearing holder 32rests on a lubricating sheet (not shown). The torque tube 14 rests inthe lower bearing half 32. An upper bearing half 34 is placed over thetorque tube 14, and a bearing cap 36 is secured to the bearing base 28with a lubricating sheet (not shown) there between. When the torque tube14 is rotated, the upper and lower bearing halves 32, 34 rotate with thetorque tube 14

The lock out device includes a shaft support 38 formed on both sides ofthe pier 18 and through which the cam shaft 22 passes. The shaft support38 is fixed to the pier 18 using a hinge 50. The cam 24, one on bothsides of the pier 18 is rigidly mounted on the cam shaft 22 and rotateswith the cam shaft 22. A follower 40 extends from the shaft support 38and rides in a groove 42 formed in the cam 24. The follower is rigidlyattached to the shaft support 38, e.g., by welding. Protruding from theother side of the shaft support 38 are one or more pins 41. The pins 41depending on the position of the cam 24, are configured to extend intoopenings 44 formed in the lower bearing half 32. Movement of the pins 41into the openings 44 of the lower bearing half 32 locks the bearing 20 aand prevents rotation of the torque tube 14, such as when wind loaded.

FIG. 3B depicts a similar lock-out device 26 used in conjunction with amass balanced bearing 20 b. Unlike the concentric bearing 20 a, the massbalanced bearing 20 b is not formed of two halves. Instead a housing 46includes an opening configured to receive the torque tube 14. A lockingmechanism 48 ensures that the torque tube 14 is secured in the opening.Below the opening, a slot 50 is formed in the housing 46 and may besemi-circular in shape extending under the torque tube 14. Rollers 52are secured to the bearing base 28 and support the housing 46 and torquetube 14 secured therein. The openings 44 are formed in the housing 46below the slot 50 and are configured to receive the pins 41 when forcedinto the opening in the shaft support 38 as the follower 40 is drivenabout the hinge 50 by the cam 24 on cam shaft 22.

Regardless of whether bearing 20 a or 20 b is employed, when the torquetube 14 is driven by a prime mover, such as the slew drive 12, thetorque tube rotates about its axis within the bearing. The cam shaft 22is also rotated at the same time and with predetermined velocity. Thepredetermined velocity is at a specific ratio to the speed of rotationof the torque tube 14 and the bearings 20 a, 20 b attached thereto. Therotation of the cam shaft 22 causes the cams 24 to rotate. The rotationof the cams 24 causes the followers 40 to move the shaft support 38 andthus force the pins 41 in and out of the openings 44 in the lowerbearing half 32 or housing 46. The cams 24 are arranged so that thefollowers 41 on each side of the bearings 20 a 20 b are forced into theopenings 44 in an alternating pattern. Due to the motion torque tube 14,and cam shaft 22 that moves synchronously therewith, followers 41 areinserted and removed from openings 44 in an alternating pattern. Theinsertion is in such a way that when, for example, a left follower 40goes in, a right follower 40 moves out and thus when the right follower40 is in, the left follower 40 is out. However, in at least oneembodiment there will always be a follower 40 inserted into an opening44 of the bearing 20 a 20 b. As will be appreciated, the tracker 100 isnot truly locked in position but rather its motion caused by windloading and other external forces is restricted to the size of theopenings 44.

Thus, in accordance with the disclosure, when the torque tube 14 isdriven by the slew drive 12 or another prime mover, the cam shaft 22will rotate and the cam 24 will smoothly insert and remove the pins 41from the openings 44. But, if the torque tube 14 tube is suddenly windloaded or another force is applied seeking to rotate the torque tube 14,that rotation is prevented by the presence of the pins 41 in theopenings 44. Movement of the torque tube 14, and therewith solar modulesis limited to the range of motion afforded by the size of the openings44. The load caused by the wind loading or other external force isabsorbed by the pins 41 and transferred via the shaft supports 38 andhinge 50 of lock-out device 26 to the piers 18 and not into the bearings20 a, 20 b. Further, this loading is shared over the number of lock-outdevices 26 employed on the tracker 100. Only two are depicted in FIG. 2,however, there could be one on every pier, every other pier, or as manyas needed to achieve the desired stiffness for the tracker 100.Regardless of the number employed, the overall stiffness of the tracker100 is increased by the use of lock-out devices 26. By increasing thestiffness of the tracker 100 the size of the components such as thetorque tube 14 and the slew drive (and the gearing associated with thedrive) can be reduced resulting in cost savings in the construction ofthe solar tracker 100.

Another benefit of the tracker 100 employing lock-out devices 26 areimproved energy production. Often wind loading is a temporaryoccurrence. As a result, there are times when despite prevailing windloading at 10-15 MPH, gusts of 20, 25, 30 and higher gusts. Inaccordance with some wind loading protection schemes, when the observedwind speed exceeds a predetermined amount for a given period of time,the tracker 100 is rotated back to a 0 degree or some shallow angleposition where the solar modules are substantially parallel to theground, and the loading caused by the wind is substantially reduced. Toachieve this the torque tube 14 must be rotated. This rotation usesenergy, and depending on the wind direction, may further increase theloading on the slew drive 12. Further, when in this stowed position,whether 0, 10, or 20 degrees to horizontal, the energy production of thesolar modules is substantially decreased. In contrast, in accordancewith the disclosure, upon experiencing loading, the tracker 100 islocked in a position that is much closer to the desired position for thesun angle at that time. Thus, energy production is only slightly, if atall, impacted by the wind event. As will be appreciated, should theduration of the event or the speed of the wind necessitate, the slewdrive 12 may still be employed to drive the tracker to a more desirableposition. While doing so, because the pins 41 will always remain engagedwith the openings 44, the loading on the tracker 100 remains borne bythe piers 18 upon which the lock-out devices 26 are deployed. Further,where the wind loading is merely transitory, as is often the case, thenthe tracker 100 may continue to be driven as normal following a returnto lesser wind conditions. These features may be further enabled by realtime wind speed sensors deployed proximate the tracker 100 and one ormore control algorithms employed to drive the slew drive 12 inaccordance with detection of the ambient and expected meteorological andweather conditions.

FIG. 4 depicts a perspective view of the lock-out device 26 mounted on apier 18 with the bearing 20 a, 20 b removed for ease of identifying thecomponents described above. FIG. 5 is a top view of the lock-out device26 mounted on a pier 18 with the bearing 20 a, 20 b removed. As can beseen clearly in FIG. 5, the cam grooves 42 are eccentric, andsubstantially parallel to one another. These parallel grooves 42 enablethe alternate movement of the followers 40 and thus the shaft supports38 with pins 41.

FIG. 6 is a perspective view of a concentric bearing 20 a with thelocking mechanism 26 and the pier 18 removed. As can be clearly seen thebearing cap 36 is bolted to the bearing base 28 securing the upper andlower bearing halves 34 and 32 therebetween.

FIG. 7 is a side view of a bearing 20 b mounted on a pier 8 with thelock-out device 26 in place. This view shows a hinge 50, which allow theshaft supports 28 to rotate about it as the follower 40 traverses thegroove 42 in the cam 24. Each shaft support 28 includes such a hinge 50.Accordingly, in at least one embodiment the pins 41 are rigidly mountedto the shaft supports 28 and as the follower 40 traverses the eccentricgrove 42 in the cam 24 the shaft support 28 is forced to rotate on thehinge 50. The result of this motion is that pins 41 mounted on the shaftsupport 38 move in or out of the opening 44 in the bearing 20 a, 20 b.Further description of this movement is depicted with reference to FIG.9, below.

FIG. 8 depicts the cyclical motion of the pins 40 as they move in andout of opening 44 in bearings 20 a or 20 b. On the x-axis is the angularorientation of the torque tube 14 and the solar modules mounted thereto. −60 on the x-axis represents a generally easterly orientation of thetorque tube 14 and the solar modules mounted thereon, while 60represents a generally westerly orientation. The torque tube transits,in this example 120 degrees of rotation from east to west. The pins 40in this example are 180 degrees out of phase with one another such thatas the torque tube 14 rotates, one follower 40 is moved from a lockedposition to an unlocked position, while the second pin is moving from anunlocked position to the locked position.

FIG. 9 depicts the motion of the pins 41 into and out of the openings 44in the housing of a bearing 20 b. In frame (a) which may roughlycorrespond to about a −50-angle position in FIG. 8, the pins 41 fromboth shaft supports 28 are engaged with the openings 44 in the bearing20 b. Frame (b) roughly corresponds to a −38 angle where the left pin 41is completely disengaged or unlocked from the opening 44 in the bearing20 b, and the right pin 41 is fully engaged in the opening. Frame (c)roughly corresponds to about a −24 deg position which is similar to thatdepicted in frame (a), again with both sets of pins 41 engaged with theopenings 44 in the bearing 20 b. Frame (d) shows the opposite of frame(b) and the left pin 41 is now fully engaged or locked into the opening44 of the bearing 20(b) while the right pin 41 is fully disengaged. Thisposition in frame (d) roughly corresponds to a −12-degree angle for thetorque tube 14 and solar modules mounted thereon. Once again, frame (e)mirrors frames (a) and (c) with the pins 41 both engaged with theopenings 44. Thus, as noted above, the ability of the torque tube 14 torotate either opposite or in furtherance of its driven position, by windor any other outside force is limited by the size of the openings 44 andthe presence of pins 41 in those openings.

While several embodiments of the disclosure have been shown in thedrawings, it is not intended that the disclosure be limited thereto, asit is intended that the disclosure be as broad in scope as the art willallow and that the specification be read likewise. Any combination ofthe above embodiments is also envisioned and is within the scope of theappended claims. Therefore, the above description should not beconstrued as limiting, but merely as exemplifications of particularembodiments. Those skilled in the art will envision other modificationswithin the scope of the claims appended hereto.

We claim:
 1. A solar tracker comprising: a torque tube; a plurality ofbearings configured to receive the torque tube; a plurality of pierseach configured to receive one of the plurality of bearings; and alock-out device mounted on one of the plurality of piers and operativelyassociated with at least one of the plurality of bearings, the lock outdevice configured to periodically engage and disengage openings formedin the bearings to limit movement of the torque tube and to transferload from the torque tube to the pier on which it is mounted.
 2. Thesolar tracker of claim 1, further comprising a cam shaft drivensynchronously with the torque tube.
 3. The solar tracker of claim 2,further comprising at least one cam mounted on the cam shaft andengaging the lock out device.
 4. The solar tracker of claim 3, whereinthe cam includes an eccentric groove configured to receive a follower ofthe lock out device.
 5. The solar tracker of claim 4, wherein thefollower is rigidly affixed to a shaft support.
 6. The solar tracker ofclaim 5, wherein the shaft support is mounted on the pier via a hinge.7. The solar tracker of claim 6, wherein one or more pins affixed to theshaft support are configured to engage one or more openings formed onthe bearing.
 8. The solar tracker of claim 7, wherein as the cam shaftand cam rotate, the follower which engages the eccentric groove causesthe shaft support to rotate on the hinge causing the pins to engage withor disengage from the openings formed on the bearings.
 9. The solartracker of claim 8, wherein a pier includes two lock-out devicesconfigured to alternately engage and disengage from the openings in thebearing.
 10. The solar tracker of claim 1, wherein the bearing is aconcentric bearing.
 11. The solar tracker of claim 1, wherein thebearing is a mass balanced bearing.
 12. A lock out device for a solartracker comprising: a shaft support; a hinge configured to connect theshaft support to a pier and allow the shaft support to rotate relativeto the pier; a follower rigidly mounted on the shaft support; and one ormore pins configured to engage one or more openings on a bearing tolimit rotation of the bearing.
 13. The lock out device of claim 12,wherein the follower is configured to be received within an eccentricgroove of a cam.
 14. The lock out device of claim 13, wherein rotationof the cam applies force to the follower and causes the shaft support tomove.
 15. The lock out device of claim 14, comprising a pair of shaftsupports, each mounted on opposite sides of the pier by a hinge.
 16. Thelock out device of claim 15, further comprising two cams, one each onopposite sides of the pier.
 17. The lock out device of claim 16, whereineach shaft support includes a follower configured to engage an eccentricgroove of a cam located on a respective side of the pier.
 18. The lockout device of claim 17, wherein the two cams are mounted on a cam shaft.19. The lock out device of claim 18, wherein rotation of the cam shaftcauses the eccentric groove formed in each cam to act on the followerand rotate the shaft support such that the pins on the shaft supportengage with or disengage from the openings in the bearing.
 20. The lockout device of claim 19, wherein the eccentric grooves of the two camscauses the pins on the pair of shaft supports to alternately engage withand disengage from the openings in the bearing.